Several cyclic peptides obtained from marine organisms have been disclosed (see for example Rudi A. et al., J. Nat. Prod., 2003, 66, 575-577: “Didmolamide A and B, two new cyclic hexapeptides from the marine Ascidian Didemnum molle”).
JP 11180997 discloses an antitumour compound of formula
which is obtained from Streptomyces nobilis. Its IC50 in Hela S3 cells is 14 nM.
Cancer is a leading cause of death in animals and humans. Several efforts have been and are still being undertaken in order to obtain an antitumour agent active and safe to be administered to patients suffering from a cancer. The problem to be solved by the present invention is to provide compounds that are useful in the treatment of cancer.